Re: [ANN] LuaJIT x64 port sponsorship program

[Mike Pall <mikelu-0912@...>]

Alexander Gladysh wrote:
> To be able to embed LJ2 into a 64-bit application would really help us.
> 
> Also, can you elaborate a bit more on what effect we should expect if
> LJ2 would use 64-bit-specific features? Would it run noticeably
> faster, for example? (Sorry, that was, probably, already discussed; a
> link would do.)

There probably won't be a significant speed difference. Having
more registers is helpful in some cases. But it won't affect most
benchmarks.

The main reason why regular C apps run faster on x64 than on x86
is due to better C calling conventions and RIP-relative addressing
(esp. helpful for -fPIC). But LJ2 code generation doesn't depend
on these for internal linkage.

The main reason why regular C apps run slower on x64 than on x86
is due to the bigger pointer size which reduces the available
memory bandwidth. But LJ2 uses 32 bit pointers for its GC objects
on both platforms.

--Mike